Local fire detection -
Fire fighting center (FFC)
The fire detection and suppression system shall
consist of automatic and manual systems.
Automatic systems are those in which as soon as
a fire is detected, an automatic response is actuated without human
intervention.
However, automatic systems shall be designed in
such a way that they can be manually actuated or manually disabled by
specialized workers when required.
Manual systems are those in which a manual
intervention is always required.
Whatever the type of detection, followed or not
by an automatic actuation of the fire fighting system, the ventilation or air
conditioning system of the building or room in which fire has been detected
shall be automatically shut down and the safety flaps of ventilation air duct
shall be triggered so as to close and minimize the natural draughting effect. In
areas protected by FM 200 or CO2 system all openings in the enclosure/room
shall also be provided with motorized or magnetic fire dampers, actuated by
fire detection system.
Automatic actuation consequent to fire
detection on electrical equipment shall always be preceded by a
de-energizing sequence except as otherwise specified.
The fire detection and control system shall be
of double nock principle and shall comprise but not limited to the following:
A -Local fire fighting center (FFC).
B -Local fire alarm
control panels (FACP).
c- Network.
d- Local Fire
Detection,
e- Specific
Maintenance Equipment.
The Contractor shall supply all maintenance
sets required for the fire detection apparatuses and particularly detector to
avoid the use of a ladder, and detector testers to allow periodic performance
check the different fire detectors.
The cables used for the fire detection system shall
be fire-resistant according to IEC 60331 or equivalent.
Local fire detection
The Contractor shall select the fire detectors suitable for each
particular fire risk, in order to detect the first sign of fire. The various
types of detectors, which can be applied, are as follows:
a- Ionization smoke detectors
i. The ionization smoke detectors are applicable
to all types of fire, from smoldering to open fires as well as solid and liquid
combustible fires.
ii. Since they can detect invisible smoke
particles, they can be used wherever open flaming fire may break out.
iii. The design of the sampling chamber shall
prevent dust and dirt ingress.
iv. Ionization smoke detectors shall generally
be used in electrical rooms and in unmanned rooms were no high hazardous
material exists.
b- Scattered light
smoke detectors
i. Scattered light smoke detectors are optical
smoke detectors, which detect visible smoke.
ii. Such detectors are of a wide range.
iii. The smoke inlet shall be adjustable so as to
optimize the selectivity in prevailing over the ambient conditions.
iv. Scattered light smoke detectors shall
principally be used in manned rooms where, for example, the smoke of cigarettes may
be an ambient feature.
c Rate of rising heat detectors
i. The thermal and rate of rising heat detectors
shall meet the most stringent requirements in severe applications.
ii. They shall particularly be used for detection
in premises and installations were breaking out of the fire is characterized by the very quick increase of temperature, circumstances in which other fire detectors would be of insufficient
effectiveness.
iii. Rate of rising heat detectors shall principally
be used indoor, in rooms, or in closed areas where hazardous materials such as
fuel oil and or Gas Fuel are handled.
d- UV/Infrared flame detectors
i. The design principle of the flame detectors
shall ensure that they can reliably detect breaking out of fire either outdoor or
in premises where due to the formation of smoke work processes, smoke detectors
alone are suitable or only of limited effectiveness.
ii. The flame detectors shall rapidly react to all
flaming fires in which carbonaceous materials are burning such as liquid fuels.
iii. The pyroelectric sensor will evaluate a specific wavelength of the hot carbon dioxide emitted by flame.
iv. Infrared flame detector shall principally be
used in fuel tank yards and in large and clear building halls.
e- Temperature
detectors
i. Such detectors shall be designed to meet the
highest requirements for detectors operating under extremely hard ambient
conditions.
ii. They shall be insensitive to the influence of
dust, dirt, and normal high ambient temperature.
iii. The temperature detectors operate on the proven
liquid temperature switch principle. The early alarm is guaranteed if, upon an
outbreak of fire, the temperature at the sensor increases relatively quickly.
iv. Temperature detectors shall principally be used
in permanently hot areas such as gas turbines hot part areas.
F - Automatic fuse plug or sprinkler protection
i. Automatic sprinkler protection consists of a fusible plug associated with to spray nozzle.
ii. Initiation of fire fighting is done
automatically in case of fire when the fuse plug melts due to increasing temperature.
iii. The selection of type and size of automatic
sprinkler shall be made with proper consideration given to such factors as
physical character of the hazard involved, drought conditions, and material
likely to be burning.
iv. Sprinkler type protection will be used
where automatic action shall be of spot type, i.e. limited to the directly
concerned area.
g- Fire push-buttons
i. The fire push-buttons (or manual call points)
are a part of the fire detection and extinguishing system.
ii. They provide a means of immediate manual alarm
and actuation of the extinguishing agent where applicable.
iii. They shall be of robust design for wet and
dusty areas with visual indication upon alarm.
iv. Operation of fire push-button shall need to
break a glass disc.
v. Push-buttons shall be installed all throughout
the plant at the justified location, whatever the related fire fighting system.
h- Local processor
i. Local processor shall be fully microcomputer-controlled and shall give clear local information in the event of an alarm.
ii. Local processor shall be addressable detection
system based on serial polling of each communication module over a two wires
line. Data and control signals can be transmitted simultaneously.
iii. With such a system, each detector and,
therefore, each area has its own address. Thus, the alarm location can be
accurately displayed and identified.
iv. The system shall be of self-diagnosis type.
v. Short circuit and open detector line shall be
identified as a fault.
vi. Local processor shall have a keyboard for entering the password, switching on or off individual detection line, switching over to
detector test mode, and entering changes of function. Each of these inputs is
also displayed in the fire fighting center.
vii. Local processor shall have a redundant power
supply and redundant communication line with the overall plant control unit.
Fire fighting center shall ensure:
a- Fast wide range information system with
guaranteed exchange timer.
Such information facility directly increases
efficiency at fire operator' stations, aids data exchange among local
processors and make easier the function reconfiguration.
a- Monitoring of the proper functioning of
connected equipment.
The fire fighting control system shall be
redundant in order to prevent total communication breakdown caused by single
failure.
The fire fighting control system shall be
distributed system data highway type to provide communication between the operator and local processor. The communication network is configured by means of a
redundant bus.
The man-machine interface shall be an ergonomic
work station with high-resolution color graphics flat screen, special control
keyboards, instinctive control by mouse (or ball), and high-speed display
appearance.
The pictures shall be linked to each other by sets so that it shall be possible to display them in sequences by pressing "next page" or "previous page" keys
.
From the fire operator work station it shall be
possible:
a] to acknowledge local alarm issued by local
processor,
b] to switch over to "detector test
mode" part of the local processor,
c] to display alarm views and alarm list,
d] to display events history,
e] to display fire fighting procedures.
A mimic diagram giving an overall view of the plant shall be installed in the fire fighting center.
It shall be located in front of the operator
workstations and shall display in a synthetic way the status of the plant.
Relevant information shall be LED color-coded.
One printer shall be dedicated to the events
and the other to the technical and fault reports.
The system shall have several kinds of
communications:
a] with the local processor,
b] with public address system for alarm,
c] with a plant control system (DCS).
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